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A study was made of the efficiency of a commercially available hydraulic dredge design in use on the west coast of Scotland and of the annual biomass production of two different razor clam (Ensis spp.) beds within the Clyde Sea area. These two parameters, viz fishing efficiency and population annual production, are fundamentally important to any proper attempt to assess the long term sustainability of a fishery. The hydraulic dredge used in this study was found to have an absolute efficiency of 90.1% when expressed in terms of the collected wet weight biomass, representing the first time that the efficiency of a hydraulic dredge of this nature has been measured rather than simply inferred from track width. This indicates that this dredge design has the potential to remove the majority of a clam population, including undersized immature individuals, within a 45 cm swath in a single tow. Annual production estimates were also made for two separate razor clam beds. One population of Ensis siliqua was located in Irvine Bay and the other two populations (one E. siliqua and one E. arcuatus) occurred in a mixed bed on Hunterston Sands. Each location was sampled quantitatively on a regular basis using the same hydraulic dredge. Dredged areas were measured by SCUBA divers so that the population densities could be calculated for each sampling event. Size-classes within each population were identified from siphonal shell breadth measurements and production estimates were calculated using a size-cohort analysis procedure designed for stocks exhibiting recruitment but that do not have separable age-classes. Production of all three populations was low during the study (1.82–18.08 g AFDW 10 m-2) as were the production/biomass estimates (0.01–0.11). These data indicate that populations of Ensis spp. on the west coast of Scotland are slow-growing and typical of K-selected species. These data highlight the conflicting pressures facing any razor clam fishery: the design of extremely efficient hydraulic gear and the slow-growth of the target species. It is clear that the future commercial exploitation of these species will need very careful management to ensure sustainability and avoid fishery over-depletion.

Results are presented of a comparative study on seasonal variations in population density, population structure and reproductive bionomics of two species of offshore benthic oedicerotid amphipod, Westwoodilla caecula (from 35 m depth) and Monoculodes packardi (from 190 m) in Loch Fyne (Scotland). Observations on live coloration and behaviour of these species in laboratory aquaria are also included. Male W. caecula were, on average, smaller than females. In M. packardi (atypically among Oedicerotidae) the reverse was true. Population densities of both species, calculated from sledge net tows (1-mm mesh), fluctuated erratically over one year (1992). Ovigerous W, caecula were recorded virtually year-round, but were commonest from midsummer to early autumn. Ovigerous M. packardi were noted in spring and early autumn. Monoculodes packardi had a semi-annual life cycle, but the pattern for W. caecula was less clear. The two generations of M. packardi grew at broadly similar rates, presumably associated with the damped seasonal fluctuations in physical environmental factors at 190 m. Female W. caecula possibly moult eight or nine times, and may produce three successive broods in a lifetime (M. packardi may only produce two). A positive correlation was found between fecundity (stage I eggs) and body length in W. caecula but, although a similar trend was apparent in the data for M. packardi, relevant data were too few for significance to be achieved. Ovoid eggs increased in volume by ×2 from stage I-IV in W. caecula, or ×1·5 from stage I–III in M. packardi. Brood sizes were much smaller in W. caecula than in M. packardi, although apparent brood mortality was higher in the latter. There was no significant relationship between the proportion of ovigerous females in the populations of either species and seasonal variation in physical environmental factors considered (temperature, salinity, daylength).

Detailed catch and life history data for Perioculodes longimanus and Pontocrates arcticus, together with more limited comparable information on Synchelidium maculatum, are reported. Samples were taken year-round using a 0–5 mm mesh D-net towed over sand in the immediate sublittoral zone (-2 to -6 m Chart Datum) in Kames Bay, Great Cumbrae Island, Scotland. Estimated population densities of Perioculodes longimanus were highest in summer. The occurrence of Pontocrates arcticus was more erratic and S. maculatum occurred only in midsummer in very low numbers. The mean sizes of all population categories of Perioculodes longimanus were bigger in summer than in late autumn and winter. Female Perioculodes longimanus parasitized with the copepod Sphaeronella minuta were significantly smaller than the whole category ‘sexable females’. Adult female S. minuta (one per amphipod brood pouch infected) carried — 70–200 eggs per sac. In both Perioculodes longimanus and Pontocrates arcticus females were larger than males. In Synchelidium maculatum, by contrast, males and females were not different in size. Gravid females were present virtually year-round in Perioculodes longimanus and Pontocrates arcticus, with particularly high proportions of ovigerous females in midsummer and low proportions in midwinter. Both of these species had an annual life cycle with only one generation per year. Longevity was estimated at 15 months. The sex ratio nearly always showed substantial female dominance in all three species. Fecundity appeared to be related to body size but, due to egg losses during sample processing, data were too few for detailed analysis. The eggs of Perioculodes longimanus and Pontocrates arcticus were elliptical in shape, with winter eggs being smaller than summer eggs in Perioculodes longimanus, but larger in Pontocrates arcticus. The percentage of ovigerous females in the population was significantly correlated with a range of environmental factors tested, the highest correlation being with maximum weekly air temperature (for Perioculodes longimanus) and daylength (Pontocrates arcticus), although causative effects cannot be established since temperature/daylength factors were not independent variables

Thirteen species of Amphipoda have been recorded from the stomachs of plaice and 11 species from dabs, with Perioculodes longimanus the most notable prey oedicerotid in both flatfish species sampled from the shallow sublittoral zone (Angulus sp.). Polychaetes were more numerous in larger plaice. Sand gobies specialized on small crustaceans, taking 13 amphipod species inter alia (with P. longimanus again the most notable oedicerotid). Amphipod numbers in sand goby stomachs increased with the length of the fish. Neither dabs nor sand gobies consumed bivalve siphon tips and only rarely consumed polychaetes. Although amphipods formed only a minor part of the diet of plaice, at the population density known for this species in this bay, its depredations would still constitute an important selective agency governing patterns of activity in epibenthic oedicerotids.

Data are presented on the density of ten species of Amphipoda and two species of Isopoda from terrestrial to aquatic (freshwater through brackish water to marine) habitats, derived using a new modification of the displacement method involving batch testing of animals and subsequent Probit Analysis of data.Surprisingly few data are available in the literature concerning the densities of marine organisms. Extensive work on this topic was published some half a century ago by A.G. Lowndes. He reported widely on crabs and lobsters (Lowndes, 1943a), echinoderms (Lowndes, 1953) and fishes (Lowndes, 1955). In his paper to the Linnean Society (Lowndes, 1938a) he included data on some of the smaller freshwater Crustacea. Gross & Raymont (1942) have published on the specific gravity of the marine copepodCalanus finmarchicus.In espousing the displacement method for dealing with live individuals (Lowndes, 1938a,b, 1942, 1943b, 1955), he dismissed summarily earlier techniques that involved ascertaining whether killed or narcotized animals sank or floated in liquids of known density. While we recognize the limitations of the old methods, Lowndes’ displacement technique, although very accurate for individuals (he quoted figures to five decimal places), is very tedious to replicate [“elegant if somewhat exacting”, according to Hutchinson, 1967] and so reliance tends to be placed on figures obtained for very few individuals, typically only one or two. Even Lowndes himself was wary of attributing significance to the last two decimal places in his estimations, since individuals will vary in density according to sex, the contents of the gut etc. (Eyden, 1923; Lowndes, 1938b; but see Fox & Mitchell, 1953).

Ferritin crystals and calcium granules are reported from the ventral ceaca of Steleuthera ecoprophycea (Amphipoda: Stegocephalidae) collected from the Snake Pit hydrothermal vent, Mid-Atlantic Ridge (3520 m).In a series of earlier papers (Moore & Rainbow, 1984, 1989, 1992; Moore et al., 1994), the authors described the widespread occurrence of intracellular, octahedral crystals of ferritin in the ventral caeca of a range of stegocephalid amphipod species from the continental shelf epibenthos and oceanic plankton. The discovery at 3500 m of a new Steleuthera species (S. ecoprophycea), from a hydrothermal vent on the Mid-Atlantic Ridge was announced recently by Bellan-Santini & Thurston (1996), and a complete description is provided therein.Oceanic ridge sites are notable for their tectonic activity and the presence of a diversity of trace metals at high concentrations is to be expected in hydrothermal plumes emanating from such regions (German & Angel, 1995). The detoxification of accumulated trace metals in the ventral ceaca of stegocephalid amphipods from uncontaminated environments is now relatively well known (see above), so it was of interest to investigate whether a vent stegocephalid showed an atypical presence of trace metals in detoxified form in cells of the ventral caeca. The results following from an opportunity to investigate this are reported herein.Material was derived from a dive made by the submersible ‘Alvin’ at Snake Pit hydrothermal field, Mid-Atlantic Ridge (23°23′N 44°56′W), 3520 m, on 16 June 1993 (see Bellan-Santini & Thurston, 1996). Steleuthera ecoprophycea was preserved in 70% alcohol. Subsequently to dissection, the single pair of ventral caeca from each of the four damaged amphipods investigated were post-fixed in 4% glutaraldehyde. For electron microscopy and x-ray microanalysis in STEM mode, ventral caecal tissues were then dehydrated through 95% and absolute ethanol, cleared in propylene oxide, embedded in TAAB resin, sectioned at 0·5 μm (semi-thin sections) on a Reichert OmU2 ultramicrotome and examined without staining in a JEOL 100C electron microscope equipped with LINK system EDX energy dispersive x-ray microanalyser.

Results of a comparative study on the distribution, growth and reproductive bionomics of two species of sand-dwelling oedicerotid amphipod, Pontocrates arenarius and P. Altamarinus are presented. Pontocrates arenarius is a littoral species with highest population densities between mean tide level (MTL) and low water springs (LWS) while P. altamarinus lives in the immediate sublittoral between LWS and -2 m Chart Datum. Both species are iteroparous, have female biased sex ratios, year-round breeding and life cycles largely based on two generations per year. The percentage of ovigerous females in the total population indicates breeding activity, and temporal changes in this percentage (arcsin transformed) have been tested for correlations against seasonal variation in five environmental factors (mean maximum weekly air temperature, mean minimum weekly air temperature, mean weekly sea temperature, day length, and mean weekly windspeed). Based on these analyses, differences in the timing of peak reproductive activity between these two species are interpreted as indicating the operation of different mortality agents, i.e. abiotic factors in the littoral P. arenarius and biotic effects (e.g. predation by fish) in P. altamarinus from the sublittoral.

Maerl grounds are comparable to sea grass beds in terms of their high biodiversity, and are characterized by abundant juveniles of species such as the queen scallop, Aequipecten opercularis. Maerl grounds impacted by towed demersal fishing gears are structurally less heterogeneous than pristine, un-impacted maerl grounds, diminishing the biodiversity potential of these habitats.

To date, the oedicerotid amphipod Monoculodes gibbosus Chevreux, 1888 is known in British seas from only two individuals collected from Loch Fyne and lodged in the Robertson Collection at Millport (Moore, 1984). Recent intensive research on other species in this family in the Clyde Sea area by one of us (D.J.B.) has resulted in the sporadic capture of further individuals of M. gibbosus (128 individuals in total) from Inchmarnock Water, southern Loch Fyne. This material allows us to expand our knowledge of the species' morphology, live colour, population structure, fecundity, egg size, breeding season, diet and behaviour. Notes on these topics are presented below.

Netted dogwhelks Nassarius reticulatus were offered standardized olfactory signals derived from flesh of: cod (Gadus morhua), starfish (Asterias rubens), shore crabs (Carcinus maenas), mussels (Mytilus edulis), periwinkles (Littorina littorea), dog whelks (Nucella lapillus) and netted dogwhelks. Nassarius reticulatus responded positively to all signals except the conspecific one. Positive responses to extracts were in the order (strongest to weakest): Gadus, Carcinus, Nucella, Mytilus, Asterias, Littorina. Starved Nassarius reticulatus buried in sand emerged rapidly to feed on crushed C. maenas, but remained buried when offered crushed conspecifics. These data confirmed the hypothesis that N. reticulatus would not respond positively to the smell of conspecific carrion, to avoid emerging from the substratum while neighbours were being predated. However, a second hypothesis, that strength of response to olfactory signal was proportional to taxonomic distance between N. reticulatus and the source of carrion was not supported by the data.

Notice is given of the presence of a previously un-reported oedicerotid amphipod species, Pontocra tes arcticus Sars, in the shallow sublittoral zone of the sandy beach at Kames Bay, Millport (Scotland). Distinguishing features from P. arenarius are the parallel-sided second coxal plates, strongly deflexed narrow rostrum and lack of sternal dark pigmentation patterns in both sexes. A key to the three species in the genus is provided.

Analysis of the total copper and zinc content of four species of talitrid amphipods, Orchestia gammarellus, O. mediterranea, Talitrus saltator and Talorchestia deshayesii throughout a complete spring/neap tidal cycle failed to reveal any significant effects of moulting upon body copper or zinc in any species. Moulting was synchronized to the lunar cycle only in T. saltator, taking place 5–7 days prior to a new moon. The fact that no significant changes in body metal concentrations took place with the moult cycle is discussed in relation to the use of talitrid amphipods in copper and zinc biomonitoring programmes.

The parasitic copepod Sphaeronella? callisomae, usually a single female, was occasionally found in the brood pouch of the amphipod Orchomene nanus. It is possible that this parasite consumes its host's eggs. Infected female hosts were significantly smaller than uninfected ones, so the copepod may retard host growth (or select young female hosts). Other associates (ciliates) were found in the body cavity and epizooitically on the host's gill lamellae.Extensive collections of Orchomene nanus (Krøyer) (Crustacea: Amphipoda) have been made year-round (April 1993 to April 1994) using funnel-traps baited with crushed shore crabs (Carcinus maenas (L.)) deployed overnight (soak time 17 h) in the shallow sublittoral (5–6 m depth) at Keppel Bight, Millport (54°45·75′N 4°54·48′W: for further details, see Moore & Wong, 1995, in press a,b).The presence of nicothoid copepods (tentatively identified by Mr M. O'Reilly, Clyde River Purification Board, as Sphaeronella? callisomae Scott; an inadequately described species, see Gotto, 1993) in the brood pouch of this amphipod were recorded routinely. At least two species of ciliates were also encountered. A sessile ciliate protozoan (?Lagenophrys sp.) occurred commonly as an epizoite of O. nanus branchiae (Figure 1A–D); and unidentified parasitic ciliates, possibly of three species, occurred in the body cavity (Figure 1E, F).The incidence of parasitization of female O. nanus with S. ?callisomae was very low (0·81%; 8/990). There was only ever a single mature female copepod per host, although instances occurred of multiple infestations with nauplii or copepodites. Two female O. nanus were recorded with a female nicothoid coexisting with the amphipod's own eggs inside the brood pouch.

Examination of a small sample of Podocerus chelonophilus found clustered around mucus-exuding epidermal lesions of juvenile loggerhead turtles (Caretta caretta) collected off Madeira revealed the presence of fibrous material in the gut contents. The absence of planktonic remains suggested that these amphipods had been exploiting turtle material directly.With the exception of the Cyamidae (whale lice), rather few amphipod taxa consistently live in association with marine vertebrates. Sea turtles, however, have been recorded carrying gammaridean and caprellidean epibionts by Caine (1986), who reported eight gammaridean species (including two domicolous fouling species) from nesting loggerhead turtles in Florida.

A hitherto unreported association between the isaeid amphipod Photis longicaudata and the hexacorallian Cerianthus lloydii is described and illustrated from material collected near Millport, Clyde Sea area. By building their tubes around the outside rim of the anemones' tubes, this amphipod presumably gains proximity protection from predators.

Material from Loch Fyne referable to Monoculodes gibbosus Chevreux (Oedicerotidae) has been discovered in the Reference Collection at Millport originally labelled by David Robertson as M. stimpsoni Bate. This is the first British record of this little known species. A detailed redescription is provided and comparison made with French material (including the holotype). A revised key to the British species is presented.

Coxal plates 1–5 of Epimeria cornigera form a closely interlocking series keyed by the head such that ventral flexion of the peraeon is severely curtailed. The clamp formed by coxae 4 and 5 is interpreted as an adaptation facilitating copulation in a species with feeble gnathopods and non-prehensile antennae. The morphology of the posterior three pairs of peraeopods can also be regarded as an adaptation for gripping the female. Other possible functions (e.g. predator deterrence and feeding grip) of coxal structures are also examined.

The amphipod family Acanthonotozomatidae was represented hitherto in British waters by the generaIphimedia Rathke (includingPanoploea Thompson) andOdius Lilljeborg; Acanthonotozoma Boeck being unrecorded (Lincoln, 1979).Material referable toAcanthonotozoma serratum (O. Fabricuius, 1780) is here reported from the East coast of Scotland. Two specimens (1 juvenile,ca. 7 mm long and 1 immature female, broken in half, estimated length 85 mm) were taken by Dr R. Earll by diving (his sample no. CR2, St. 4/3) from amongst tubes occupied by the amphipodEricthonius rubricornis Stimpson attached to boulders amongst coarse sand, depth 345 m, at Coldingham Bay, St Abbs, Berwickshire, Scotland (55° 53' 30": 2° 5' 36") on 17 August 1982. Dr Earll kindly made over his amphipod material to me for identification.Just (1978) has reviewed the genusAcanthonotozoma and has commented on the variability of both morphology and coloration ofA. serratum from Greenland, Iceland, Spitzbergen, Russian Kara Sea, N. Norway and the Skagerrak. The Scottish material has Norwegian rather than Greenlandic characteristics. Thus the dorsal tooth on peraeonite 5 is lacking, giving the dorsum a 4-dentate appearance. Coxal plate 3 is bluntly tapered distally. Coxal plate 4 is squarish and coxal plate 7 has the posterodistal corner unproduced. The posterodistal projections of the third epimeral plate are short with a wide angle between them. The basal articles of peraeopods 57­ have a square, less sharply produced posterodistal corner.Mouthparts and anterior peraeopoda have been dissected from the right side of the female and mounted on three slides in polyvinyl-lactophenol. No significant differences are apparent in mouthpart morphology compared with fig. 4 in Just (1978).

Recently, I wrote (Moore, 1978) that no substantiated records existed forCorophium sextonaeCrawford amend. Hurley (Amphipoda) north of Abereiddy Quarry, S. Wales. The records of the species for the West coast of Scotland given by Scarratt (1961, Ph.D. Thesis, University of Wales) have been regarded as suspect on the basis of wrongly labelled material from his type collection now (with his kind permission) in my possession. My own investigation of amphipods from kelp holdfasts in the Clyde Sea area and its environs, over many years have failed to produce this species.C. sextonaehas now, however, been identified with certainty from a collection (made on 6 September 1979) ofAscidia mentulaMuller taken from a rope suspended (on 26 April 1979) from the U.M.B.S. raft in Linne Mhuirich, a marine lake off Loch Sween, lat. 55° 59′ N, long 5° 39′ W, O.S. ref. NR732853. Both male and ovigerous femaleC. sextonaewere included in the material. They were living in silty tubes attached to the tests of the ascidians, together withJassa falcata(Montagu) andMicrodeutopus anomalus(Rathke).Personal collections of kelp holdfasts and other algae (Codium, ‘red algal turf’ mostlyBonnemaisonia) in the nearby rapids (ca. 3·2 km distant) at Linne Mhuirich in May 1969 (Moore, 1971, Ph.D. Thesis, University of Leeds) and in June 1974 (Shillaker & Moore, 1978) failed to disclose anyC. sextonae(allCorophiumwereC. bonnellii).C. sextonaemay be very localized within Linne Mhuirich, given Moore's (1978) observations on Lundy; the acknowledged unique hydrography of Linne Mhuirich (Kerr, 1912; Lewis & Powell, i960) and the sensitivity of the species to water movement gradients (Hughes, 1975).

During a recent preliminary survey of the Clyde deeps using a 0–5 m D-net (mesh ca. 1 mm, 26 mesh per inch), three little known species of Amphipoda were collected. Amphilochoides boecki Sars (Amphilochidae) was taken over a consolidated sand Dentalium ground inside Sgat Mhor, Ascog Bay, Lower L. Fyne on 3 July 1980 from a depth of 36 m. This species has been recognized as distinct from A. serratipes (Norman) by Lincoln (1979) who noted that no British material of A. boecki had been confirmed to date. This therefore represents the first British record of the species. Eriopisa elongata (Bruzelius) (Melitidae) was taken from 150 m between Cumbrae and Arran in the Clyde in 1885 by Canon A. M. Norman. Earlier (1866) dredgings with Gwyn Jeffreys in the Sound of Skye had first brought this species to light in British waters (Norman, 1889). I am not aware of any published record of E. elongata in the Clyde area since that time and it is not known from anywhere else in Britain (Lincoln, 1979). The species (two individuals) was taken in 118 m over a soft mud bottom off Holy Isle (Arran) on 3 July 1980. Dyopedos monacanthus (Metzger) (Podoceridae) has been taken once previously in the Clyde, from the stomach of a haddock in 1897 (Scott, 1901 as Dulichia monacantha Metzger), a record not included in Lincoln's (1979) latest review. Two individuals were captured on 2 July 1980, over soft mud, from 183 m off Tarbert, Lower L. Fyne.